The Salk Institute for Biological Studies will unveil today the first major fundraising campaign in its 53-year history, hoping to bring in $300 million to support scientists who are struggling with a nationwide slide in federal research grants.

The nonprofit institute has raised $140 million during the quiet period of the campaign, which is meant to build credibility and momentum as well as cash. The supporters include a group of donors from business, science and the arts who’ve recently made $16 million in gifts.

But Salk officials say they’re going to have to press hard through June 2015 to raise the balance of the money in a campaign largely meant to double Salk’s $200 million endowment, and to ensure that all 35 of its chief scientists have endowed professorships. The interest from such endowed positions helps pay for research.

Salk, which has done research ranging from new cancer drugs to crop yields, is operating in the black financially. But there’s concern that the institute’s $100 million budget could be reduced by $10 million because of cuts to public research funding. Salk is making virtually no effort to raise funds for another need — buildings.

“We are looking to provide more long-term stability in the face, perhaps, of decreasing support on the federal and state level,” said Qualcomm co-founder Irwin Jacobs, who is chair of Salk’s board of trustees. “In the past (Salk) has relied very heavily on federal funding. But now, with fewer grants being given, there’s uncertainty.”

A decade ago, two-thirds of Salk’s federal backing came from the National Institutes of Health, the country’s largest public underwriter of basic biomedical research. Salk says it now gets less than half of its federal funding from NIH.

The NIH budget, which exceeds $30 billion, has been largely flat in recent years, and the agency is receiving record numbers of grant applications. The percentage of NIH applications funded last year was 18 percent, down from 30 percent about 10 years ago.

The competition for money is intense, and some of it comes from Salk’s powerful neighbors. Salk is in an area of La Jolla that’s also home to UC San Diego, the Scripps Research Institute, the Sanford-Burnham Medical Research Institute, the J. Craig Venter Institute, and the La Jolla Institute for Allergy & Immunology. All of these centers do some of the same type of basic biological research for which Salk has become famous.

Everyone is feeling the pinch. Ann Carollo, senior vice president for external relations at Sanford-Burnham, said Wednesday that the institution also is seeking philanthropic support.

“Independent free-standing research institutions like Sanford-Burnham, the Salk and the Scripps Research Institute are particularly challenged at this time,” she said. “We have to manage with fewer — and smaller — government grants.”

Salk was founded in 1960 by Jonas Salk, who developed the first polio vaccine. The institute quickly established an international reputation, largely because it hired such luminaries as Francis Crick, who had co-discovered the structure of DNA, and Renato Dulbecco, who won a Nobel Prize for his insights on how cancer takes hold.

Like other Salk researchers, they focused on the basic nature of life, mostly leaving it to others to find a use for their findings. The institute often points to the work of geneticist Tony Hunter, whose research has helped lead to the creation of dozens of new drugs, including Gleevec, which is used to fight cancer.

But the focus on basic research also poses serious financial challenges, especially when it comes to the need to raise lots of private money.

“The hard thing is to get people to fund things that increase knowledge but which aren’t necessarily targeted at specific diseases,” said William R. Brody, Salk’s president.

M. Faye Wilson, a member of Salk’s board of trustees, also sees that as a challenge, which recently led her to make a $1 million donation to Campaign for Salk, which is what the undertaking is being called.

“This country has been cutting edge in science for a long time because of basic research made at places like Salk,” said Wilson, chief executive of Wilson Boyles & Co., a business management consulting firm. “Without basic research, we wouldn’t have the discoveries and cures and treatments that benefit a wide spectrum of people today.”